The present invention relates to direct Human-Computer neural interfaces, i.e. controlling of computers to perform various functions through human thought transmitted to computers as electrical signals.
Controlling computers with human thought, i.e brain waves, is no longer science fiction. Considerable work has been done with severely paralyzed persons who may not even have consistent head movement. Conventionally, the person""s neural activity or brain waves may be monitored through the use of an electroencephalograph (EEG) which monitors the brain through an electrode cap mounted on the head.
Computers have already been controlled in a basic or rudimentary way through the measurement of the electrical activity of the human brain. The EEG records the voltage fluctuations of the brain which can be detected using electrodes attached to the scalp. The EEG signals arise from the cerebral cortex, a layer of highly convoluted neuronal tissue several centimeters thick. It is believed that the pyramidal cells of the cerebral cortex are the source of the EEG voltages. Each of these pyramidal nerve cells constitutes a tiny current dipole with a polarity that depends on whether the net input to the cell inhibits or excites. As a result, this dense layer of pyramidal cells produces a constantly shifting configuration of electrical activity as the nerve impulses change. The measurements on the scalp can detect the underlying electrical patterns in a form that is somewhat dulled by passage through the skull. For many years, researchers have tried to correlate the EEG signals with particular human behaviors and sensations. This work has resulted in a functional map of the human cerebral cortex. This map now enables experimenters to specifically tailor EEG experiments by placing electrodes on the parts of the scalp directly over the source of the activity to be monitored. In order to use this electrical activity to operate a computer, workers have tried to isolate specific EEG signals that people may be able to vary and adjust at will. Commonly, EEG signals are continuously monitored with unwanted components being filtered out.
In distinguishing wanted from unwanted components of these continuously monitored EEG signals, developers have categorized the waves by the frequency of their emanations: Alpha waves (8-13 Hz) that can be effected if the user concentrates on simple mentally isolated actions like closing one""s eyes; Beta waves (14-30 Hz) associated with an alert state of mind; Theta waves (4-7 Hz) usually associated with the beginning of sleep or a xe2x80x9cdownerxe2x80x9d mental state brought on by frustration or disappointment; and Delta waves (below 3.5 Hz) associated with deep sleep. Most attempts at computer control try to use the Alpha waves because users can learn to change the amplitude of Alpha waves by concentration, raising attention and isolation from other thoughts. Users have been enabled through the focusing and unfocusing of their attention to create EEG sensed Alpha waves sufficient to move and control a cursor on a computer screen. Once it becomes viable to, thus, control a computer, it also becomes viable to then use the computer to control various computer controlled mechanical and electronic functions.
Similar work is being done with neural activity from sources other than the brain. Electromyographic (EMG) sensors are attached to the person""s skin to sense and translate muscular impulses to control computer functions. Patients have been reported to have moved objects on computer screens via EMG sensed tensing and untensing of facial muscles. Also Electrooculargraphic (EOG) signals have been sensed from eye movement and its use demonstrated to have moved items on a computer in a relatively rudimentary fashion.
The publication, Controlling Computers with Neural Signals, Hugh S. Lusted et al., Scientific American, October 1996 Issue, describes the above background material in greater detail. The authors are principals of Biocontrol Systems Inc., developers of systems in this technology.
While past use of neural signals to control computers has been primarily directed to the physically impaired, most of the research work is and will be applicable to control computers for other functions. For years, military developers have been exploring xe2x80x9cno handsxe2x80x9d computer control involving the sensing of neural signals. Such techniques are being developed for combat and other pilots.
An article, Controlling Computers by Thought, Toby Howard, published in Personal Computer World, February 1999, reports that tiny electrodes the size of a pen tip have been successfully implanted in people""s brains in areas associated with specific neuromuscular activities. These electrodes called neurotropic electrodes need no internal wires for powering; they are powered by an induction coil worn in a user""s cap. The signals from these electrodes are detected and amplified by a tiny receiver under the skull and transmitted to control a computer that the user learns to do via biofeedback. This device produces a signal that is an improvement over the EEG signals because unlike the EEG the signals are not muffled by passage through the skull.
While direct neural interfaces between humans and computers for productive purposes outside of the physically impaired functions is in its infancy, it may be reasonably expected to increase in its applications. Since the neural human-computer interface is likely to be used to control mechanical and electrical functions, it should be understood that falling asleep by the user during neural control operations could produce undesirable and even disastrous results. During the sleep state, the neural activity would still continue to be monitored and produce involuntary signals leading to the unintended results.
Accordingly, the present invention seeks to circumvent the sleep problem by providing in a system for tracking neural activity in a user and using an electrical signal based on the tracked activity for controlling computer controlled functions, an implementation for preventing neural activity during said user""s sleep from being used for controlling said functions. The present invention comprises the combination of means for predetermining a neural activity pattern indicative of the transition of a user from awake to asleep, means for monitoring the neural activity of the user for the predetermined neural activity pattern and means responsive to the detection of said predetermined neural activity pattern for terminating said use of said electrical signals. A convenient implementation for monitoring is through an EEG monitor. In one operative embodiment, the means for terminating should terminate use of electrical signals when said EEG monitor reading drops below 7 Hz, which is a conventional sleep threshold. However, it should be recognized that since sleep patterns will differ from person to person, the most accurate results may be achieved when the means for predetermining the neural activity pattern determines a specific signature pattern for each user based upon preliminary EEG testing on said user.
The present invention comprehends an implementation wherein means are provided proximate the user for the tracking of neural activity and there are means for transmitting the electrical signal to a computer remote from the user for controlling the computer controlled functions. In such an implementation, the means for transmitting said electrical signals are preferably wireless means.